Eco-Warriors

The Department of Defense has set a goal of supplying 25 per cent of the military's energy from renewable sources by 2025 (see "The Pentagon's green offensive"). The navy is even more ambitious, planning for 50 per cent renewables by 2020. While saving the environment isn't the Pentagon's main goal, military investments could foster innovations in clean energy that would ripple through civilian society. There are precedents: both the internet and the GPS technology used by your smartphone began life as US military projects.

The Pentagon's spending plans must be approved by the US Congress, however, and the navy's targets for biofuels are a huge bone of contention. While lawmakers from oil and gas-producing states are leading the opposition, even advocates for green energy worry that it's too early to know which biofuel technologies - if any - will deliver real environmental benefits when produced on a commercial scale.